Jiamin Tian

Influence of surfactant addition on rheological behaviors of injection-molded ultrafine 98W−1Ni−1Fe suspension

Abstract Ultrafine 98W-1Ni-1Fe powder injection molding was studied. The influence of ball milling and stearic acid (SA) addition on ultrafine powder characteristics and feedstock rheological behavior was investigated systematically. Results show that ball milling and SA addition can effectively increase powder loading of feedstock. SA addition can also avoid surface interactions between powder and binder during feedstock preparation, thus shortening the mixing time. SA addition is effective in reducing feedstock viscosity, but this effect decreases with increasing temperature and becomes disadvantageous when temperature is higher than 125 °C. SA addition can also reduce the temperature required for injection molding. The feedstock of powder with SA addition gets its best shear stability and lowest viscosity at 115 °C, while the feedstock of powder without SA addition obtains its best shear stability and lowest viscosity at 135 °C. Meanwhile, the former has lower temperature sensitivity and better comprehensive rheology than the latter, so the former is more suitable for ultrafine 98W-1Ni-1Fe injection molding.

Influence of ball milling on powder characteristics and feedstock rheological behaviours of injection moulded ultrafine 98W–1Ni–1Fe

Abstract In the present study, powder injection moulding (PIM) was used to fabricate ultrafine 98W–1Ni–1Fe preform. The influence of various ball milling times (3, 5 and 10 h) on the characteristics of the ultrafine powder and the rheological behaviour of the injection moulded feedstocks has been investigated over the 105–145°C temperature range and the 1·79–596·1 s−1 shear range. The results show that all the feedstocks exhibit pseudoplastic flow behaviour. The increase in ball milling time could reduce the viscosity of the feedstock and enhance the shear stability by greatly diminishing the agglomeration of ultrafine particles. However, the powder ball milled for 5 h can produce a feedstock with better thermostability and comprehensive rheology. Therefore, compared with the powder ball milled for 3 and 10 h, the powder milled for 5 h is more suitable for ultrafine 98W–1Ni–1Fe PIM.